$(document).ready(function() {
	window.onbeforeunload = function(){
		var
		h = $(window).height(),
		s = $(window).scrollTop(),
		m = $(document).height(),
		p = s ? Math.round(s/(m-h)*100) : 0;
		$.ajax({
		    url:  'spg.php',
		    data: 'spg='+p,
			async: false,
			type: 'POST'
		});
	};
});